Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal-oxide-semiconductor field-effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charge-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Electronic devices commonly include transient voltage suppression (TVS) diodes coupled in parallel with a load. The TVS diode shunts transient voltage spikes away from the load through the TVS diode to protect the load. One problem with TVS diodes is that TVS diodes can contribute to the generation of unwanted harmonics in electronic devices. Harmonics generated by TVS diodes are especially problematic when used near radio frequency (RF) signal paths or power lines. A harmonic is a signal or waveform with a frequency that is an integer multiple of the fundamental frequency. Thus, for a signal with a frequency f, the second harmonic frequency is 2f, the third harmonic is 3f, and so forth.
If enough energy is contained within the generated harmonic signals, the harmonics can cause significant interference and distortions of the primary waveform on the RF or power lines at the fundamental frequency. Harmonics, particularly odd harmonics, are generated due to nonlinearities. In the case of TVS diodes, there is a non-linear dependence of capacitance on reverse voltage (dCj/dVR) because TVS diodes are solid-state, silicon avalanche devices that are constructed with one or more p-n junctions. The width of the depletion region of a p-n junction changes with voltage, thus causing a non-linear change in capacitance of the TVS diode.
A need exists to reduce harmonic generation of TVS diodes by generating a more linear capacitance value of the device.